As Apple moves from IBM's and Freescale's PowerPC RISC architecture to Intel processors, developers must rebuild their products to support both platforms, into what Apple calls a UB (Universal Binary). And while Apple lists over 1000 UB applications currently available, this process is challenging developers, especially those of some of the largest and most critical applications for the platform.

is that not only do you have to move your code to xCode, but that as of right now, only one compiler is really supported in XCode, and that's GCC. So not only do all the developers have to port their code ot use XCode's build environment and process, but they also have to use a totatly different compiler that almost no comercial software developer uses.
From this and other articles I've read, the developers that are the most vocal about it are the ones who don't use gcc. Not that it's their fault, GCC didn't even exist when many of these projects were born. And gcc also generates sub-optimal code for the PPC. Codewarrior still generates the fastest PPC code (especially for G4s) so it's not really a question as to why they didn't switch until they were forced to.

"For apps that use Carbon, however, there is an alternative. Intel is porting their compilers (including C and C++) to Mac OS (as a plug-in for the Xcode environment, as I understand it.) But the Intel compiler will not generate PPC code, so it won't be able to produce universal binaries. It will generate Intel-only applications."

Wow, so we'll end up with Universal binaries for Xcode, and Intel or PPC versions for others. Hmm.

Also: "CodeWarrior is essentially out of business on the desktop and is now focused on embedded processors. After their unfortunately timed decision to sell off their Intel compiler technology mere months before Apple's announcement of the switch last summer" Ouch.